In conventional imaging of moving objects, the motion of the object is frozen using very short exposures in order to prevent image degradation caused by motion blur. However, because shortening the exposure may need to be compensated for by increasing illumination power, such an imaging approach may require a flash strobe or other illumination source. Accordingly, conventional imaging approaches may become useless in scenarios when the use of additional illumination is either impossible, for example when the object is a long distance away, or undesirable. Regardless of the underlying reasons, such situations can be referred to as low light conditions.
Imaging of moving objects in low light conditions can be accomplished using orthogonal transfer charge-coupled device (OTCCD) sensors. For example, image stabilization systems using OTCCD sensors can stabilize the projection of a moving object onto the sensor by shifting the sensor's array so as to counter the motion without physically moving the sensor chip. This image projection stabilization can be performed by a control system that optically measures the actual location of the moving subject in the image and shifts the OTCCD array in real time to track the motion of the subject projection onto the sensor as close as possible.
Image stabilization systems using OTCCD sensors, however, may also include an additional (e.g., tracker) sensor (e.g., a CCD or CMOS sensor) that is used to optically track the moving object projection onto the sensor surface. That is, such image stabilization systems may include two different, separate sensors (e.g., arrays): a tracker sensor that tracks the moving object, and an OTCCD (e.g., target) sensor that forms the stabilized image of the moving object.
Accordingly, the energy of the light arriving from the moving object must be split into two duplicate images for the two different sensors, with one image projected onto the tracker sensor and the other image projected onto the OTCCD sensor. However, in low light conditions, only a limited amount of energy may arrive from the moving object, and splitting the arriving energy divides this limited amount of energy even further between the two sensors, which can adversely affect the performance of the sensors. For example, diverting part of the available energy to the tracker sensor can deprive the OTCCD sensor of some of the available energy (e.g., photons), which can result in the need to extend (e.g., increase) the exposure time of the OTCCD sensor. Further, special optics (e.g., beam splitters) may be needed to split the arriving energy, which can increase the size, cost, and/or complexity of the image stabilization system.
Additionally, such image stabilization systems may be unable to produce useful images of multiple objects moving in different directions. Rather, such image stabilization systems may only be able to produce useful images of a single moving object.